Selectin-dependent adhesive events provide essential contributions to leukocyte trafficking in immune-mediated disposition of pathogens. Selectin-dependent adhesion may also contribute to delivery of natural killer (NK) cells and other immune cells to tumors, and may thereby facilitate NK cell-dependent elimination of cancer cells in vivo. The selectin-selectin counter-receptor couple may also control cell growth and differentiation in the marrow, since selectin ligand deficiencies are associated with aberrant myeloid cell proliferation. The alpha (1,3) fucosyltransferases Fuc-TIV and Fuc-TVII catalyze fucosylation events essential to the elaboration of active selecting ligands. These enzymes are thus in a position to control leukocyte trafficking events, and myeloid proliferation processes. To more completely understand the molecular of how these two enzymes contribute to (i) selectin counter-receptor synthesis, activity, and structure, (ii) myeloid cell proliferation, and (iii) leukocyte trafficking, four specific aims are proposed. Specific Aim #1 will define the structures of the glycans whose synthesis is catalyzed by Fuc-TIV and Fuc-TVII, in high endothelial venules, and in leukocytes. This work will use radiolabeled monosaccharides, and strains of mutant mice with constitutive or conditional defects in fucosylation of selectin ligands and corresponding defects in selectin ligand activity (collaboration with Dr. Minora Fukuda, Project I). Specific Aim #II will define the expression patterns of Fuc-TVII, and E- and P-selectin ligand activities, during myeloid differentiation, to begin to understand the aberrant proliferation observed in the myeloid lineage in the absence of selectin ligand activity Fuc TVII-expressing, marrow-derived myeloid progenitors will be identified using mice where the green fluorescence protein gene has been installed within, and is expressed under the control of the Fuc-TVII locus. Specific Aim #III will explore a synthetic interaction between Fuc TVII and a beta (1,4) GalNAc transferase that may modify selectin ligand structure and activity in the T lymphocyte lineage. These studies will be completed using mice deleted for the beta (1,4)GalNAc locus, and using mice where the blue fluorescence protein gene has been installed within, and is expressed control the control of the beta (1,4)GalNAc locus. Glycan structural analyses will complement these studies (collaboration with Dr. Minoru Fukuda, Project I). Specific Aim #IV will determine the role of selectin ligands, and other adhesion molecules, in the ability of NK cells to kill cancer cell in vitro and in vivo, to traffic to tumors in vivo, and to suppress tumor growth in vivo.